A desperate hunt to locate Col Muammar Gaddafi is under way amid fears he was
preparing to flee overseas.

With his 42-year regime in tatters and three of his sons detained by the rebels, the dictator's whereabouts remained unknown.

In his final hours in charge an increasingly desperate Gaddafi took to the airwaves, telling his supporters: "I am in Tripoli. Go out. I am with you until the end."

But the audio broadcast was not accompanied by pictures, fuelling speculation that he had already fled the capital and was attempting to seek exile in a sympathetic country.

The 69-year-old dictator has not been seen in public since May and his last television appearance was more than two months ago, when he was pictured playing chess against the World Chess Federation President Kirsan Ilyumzhinov.

Nato intelligence operatives were using the "full array" of surveillance equipment available in a bid to pinpoint Gaddafi's exact location.

A large number of RAF and other Nato reconnaissance aircraft are now over Libya looking for the dictator and other regime leaders.

RAF Awacs airborne radar are believed to be tracking all civilian aircraft leaving Tripoli and elsewhere in case Gaddafi tries to flee by air.

Meanwhile US Rivet Joint spy aircraft will be monitoring all communications by mobile or satellite phone.

Intelligence sources have however admitted that Gaddafi has been "extremely clever" in avoiding using of telephones knowing it could instantly pinpoint his position.

In addition RAF Sentinel reconnaissance aircraft will use their sophisticated Astor radar to track vehicle convoys heading into the desert.

In a meeting of the National Security Council, chaired by David Cameron, ministers asked for the military to "utilise all ISTAR (Intelligence Surveillance, Target Acquisition, and Reconnaissance) assets" to find Gaddafi.

"We don't know when we might find him but he can rest assured, every eye we have is looking for him," said a Whitehall source.

Pentagon officials have said they believe Gaddafi remains in Libya for the time being, but the feeling among the rebels is that he has already left Tripoli.

With an International Criminal Court (ICC) warrant out for his arrest and few allies in the world, Gaddafi's options for exile are limited.

Any nation that is signatory to the ICC is duty bound to hand him over to the authorities at The Hague.

However the Daily Telegraph has learned that despite official denials, South Africa has agreed to play a role in negotiating Gaddafi's exit strategy from Libya.

Not only is it one of most influential countries in the African Union, but its President Jacob Zuma was appointed the AU's chief mediator in the crisis and has visited Gaddafi twice since hostilities began in February.

A South African air force plane was last night on standby in Tunisia and according to sources the government is prepared to facilitate his safe passage out of the region if he decides to flee.

"We are not going to walk away from this," the source told The Daily Telegraph. "It's larger than the question of Gaddafi the person. It's a question of the unity of the Libyans and the maximum chance being created for that process to happen," the source added.

South Africa and other AU members are expected to meet to later this week with the source warning of a strong feeling that Nato exceeded the terms of the UN resolution for a no-fly zone to protect civilian life.

But Maite Nkoana-Mashabane, South Africa's foreign minister has rejected any suggestion that South Africa itself might be a venue for Gaddafi in exile.

The country, which has previously hosted former Haitian leader Jean-Bertrand Aristide and deposed Madagascan president Marc Ravalomanana, is a signatory to the ICC.

Countries that are not bound by the international agreement include Cuba, Russia and Zimbabwe, but Gaddafi's relationship with their leaders in uncertain.

Venezuela has also been touted as a likely destination as the socialist president, Hugo Chavez, is a long time friend of Gaddafi who has condemned Nato operations in Libya as nothing more than an attempt to seize control of the country's vast oilfields.

In February William Hague, the foreign secretary, confidently claimed he had learned Gaddafi was on his way to Venezuela, following the fall of Benghazi.

But hours later Mr Hague was left red faced when the Libyan leader appeared on television telling his supporters: "I want to show that I'm in Tripoli and not in Venezuela. Do not believe the channels belonging to stray dogs."

With thousands of miles of hidden tunnels criss-crossing Libya, Gaddafi and his supporters would be able to move quickly and undetected around Tripoli and beyond.

The tunnels were built in the mid-1980s as part of a vast irrigation project, but intelligence experts believe they have been used more effectively as a way of transporting troops and weapons around the country.

If Gaddafi has left Libya, one of the most likely places for him to head would be to the western city of Sirte, where he was born and where he still enjoys widespread support.

The city, which lies between Tripoli and Benghazi, is regarded as a potential site for a last stand if Tripoli falls.

Last week a US destroyer in the Mediterranean detected the launch of a scud missile from Gaddafi's stronghold in the city.

It is feared Gaddafi could have stockpiled weapons in Sirte and will use against his own people if backed into a corner.

Another possibility is that Gaddafi could have headed for his ancestral home of Sabha in the south of Libya.

From there he could possibly make an attempt to cross the border into Libya's southern neighbour of Chad.